'\" te
.\"  Copyright (c) 2006, Sun Microsystems, Inc.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
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.TH QBUFCALL 9F "Jan 16, 2006"
.SH NAME
qbufcall \- call a function when a buffer becomes available
.SH SYNOPSIS
.nf
#include <sys/stream.h>
#include <sys/ddi.h>



\fBbufcall_id_t\fR \fBqbufcall\fR(\fBqueue_t *\fR\fIq\fR, \fBsize_t\fR \fIsize\fR, \fBuint_t\fR \fIpri\fR,
     \fBvoid\fR(\fI*func\fR)(\fBvoid\fR \fI*arg\fR), \fBvoid\fR \fI*arg\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI).
.SH PARAMETERS
.ne 2
.na
\fB\fIq\fR\fR
.ad
.RS 8n
Pointer to \fBSTREAMS \fRqueue structure.
.RE

.sp
.ne 2
.na
\fB\fIsize\fR\fR
.ad
.RS 8n
Number of bytes required for the buffer.
.RE

.sp
.ne 2
.na
\fB\fIpri\fR\fR
.ad
.RS 8n
Priority of the \fBallocb\fR(9F) allocation request (not used).
.RE

.sp
.ne 2
.na
\fB\fIfunc\fR\fR
.ad
.RS 8n
Function or driver routine to be called when a buffer becomes available.
.RE

.sp
.ne 2
.na
\fB\fIarg\fR\fR
.ad
.RS 8n
Argument to the function to be called when a buffer becomes available.
.RE

.SH DESCRIPTION
The \fBqbufcall()\fR function serves as a \fBqtimeout\fR(9F) call of
indeterminate length. When a buffer allocation request fails, \fBqbufcall()\fR
can be used to schedule the routine \fIfunc\fR to be called with the argument
\fIarg\fR when a buffer becomes available. \fIfunc\fR may call \fBallocb()\fR
or it may do something else.
.sp
.LP
The \fBqbufcall()\fR function is tailored to be used with the enhanced
\fBSTREAMS \fRframework interface, which is based on the concept of perimeters.
(See \fBmt-streams\fR(9F).) \fBqbufcall()\fR schedules the specified function
to execute after entering the perimeters associated with the queue passed in as
the first parameter to \fBqbufcall()\fR. All outstanding timeouts and bufcalls
must be cancelled (using, respectively, \fBquntimeout\fR(9F) and
\fBqunbufcall\fR(9F)) before a driver close routine can block and before the
close  routine calls \fBqprocsoff\fR(9F).
.sp
.LP
\fBqprocson\fR(9F) must be called before calling either \fBqbufcall()\fR or
\fBqtimeout\fR(9F).
.SH RETURN VALUES
If successful, the \fBqbufcall()\fR function returns a \fBqbufcall\fR \fBID\fR
that can be used in a call to \fBqunbufcall\fR(9F) to cancel the request. If
the \fBqbufcall()\fR scheduling fails, \fIfunc\fR is never called and \fB0\fR
is returned.
.SH CONTEXT
The \fBqbufcall()\fR function can be called from user, interrupt, or kernel
context.
.SH SEE ALSO
.BR allocb (9F),
.BR mt-streams (9F),
.BR qprocson (9F),
.BR qtimeout (9F),
.BR qunbufcall (9F),
.BR quntimeout (9F)
.sp
.LP
\fIWriting Device Drivers\fR
.sp
.LP
\fISTREAMS Programming Guide\fR
.SH WARNINGS
Even when \fIfunc\fR is called by \fBqbufcall()\fR, \fBallocb\fR(9F) can fail
if another module or driver had allocated the memory before \fIfunc\fR was able
to call \fBallocb\fR(9F).
